1. Field of the Invention
This invention relates to mechanical stacking apparatus.
2. Description of the Prior Art
In the corrugated box industry, sheets of ribbed and flat paperboard material are first glued together to produce the characteristic corrugated structure. A conveyor is then commonly used to move these sheets to a platform where they are stacked for convenient shipment or in plant storage. The industry uses what is commonly called a double downstacker, which consists of two stacking platforms and two conveyors stacked one above the other. The advantage of the double downstacker is that two lines of articles or sheets may be handled at the same time with the need for little additional space.
A major problem concerning the use of these double downstackers which has plagued the industry since their inception is one of jamming. If too much or too little glue is initially used to form the corrugated paperboard material, the board will often separate and curl just as a normal piece of paper. If this happens on the lower conveyor, the curled board invariably catches in the conveyor apparatus thereby jamming the double conveyor system. The cutter and conveyors must then be shut down and the jammed boards removed. This process is difficult because the two conveyors are generally spaced close together vertically thereby providing little room to work. Additionally, each shutdown needed to unjam the conveyors constitutes a significant waste of time, energy and money.
These shutdown periods and the amount of time, energy and money they require are substantially lessened by the present invention. By providing means for moving the upper conveyor relative to the lower conveyor, the present invention significantly reduces the time and energy needed to remove the defective or jammed boards thereby also reducing the accompanying loss of production and money.